Control arrangement for a self-advancing pit prop unit



United States Patent Inventor Hans Rieschel Essen, Germany Appl. No, 764,455 Filed Oct. 2, 1968 Patented Dec. 1, 1970 Assignee Bergwerksverband G.m.b.H. Essen, Germany a company of Germany Priority Oct. 11, 1967 Germany No. 1,583,070

CONTROL ARRANGEMENT FOR A SELF- ADVANCING PIT PROP UNIT 4 Claims, 4 Drawing Figs.

U.S.Cl t. 91/189, 61/45, 91/1, 137/38 1nt.Cl ..Fl5b 11/16, F 15b 13/06 Field of Search 92/5;

91/1.l89; 61/45.2(Cursory), (lnquired); 74/5.43(Curs0ry); 33/2153, 206.2(A), 206.5, 207; 137/(lnquired), 38, 625.46; 1l6/(lnquired); 73/(lnquired) [56] References Cited UNITED STATES PATENTS 749,990 1/1904 Holinger 137/625.46 1,379,799 5/1921 Carman et al. 91/1 1,934,774 11/1933 Sperry, Jr. et al. 74/5.43 3,319,531 5/1967 Sanders 137/625.46X 3,436,922 4/1969 Irresberger et a1 91/1X 3,437,010 4/1969 Jacobi et al 9 l/lX Primary Examiner-Martin P. Schwadron Assistant Examinerlrwin C. Cohen Attorney-Malcolm W. Fraser ABSTRACT: An automatic system for controlling the angular settings of pit props comprising a plumb or pendulumlike device operating as a switch for causing motive fluid to actuate one or another power ram for adjusting the angle of the pit prop. The switch has a cover which supports the fulcrum pin for the plumb and the motive fluid flows through a port in the switch cover and through the fulcrum pin to passages which when pit prop adjustment is required, will deliver power to th control rams Patented 1,170

IINVENTZOR lllllll.

CONTROL ARRANGEMENT FOR A SELF-ADVANCING PIT PROP UNIT BACKGROUND OF THE INVENTION The basic form of control arrangement above-described has the advantage that even slight deflections of the plumb lead to the production of a corresponding adjusting signal, and that the pneumatic adjusting signal can be generated using the compressed air facility which is always available in a mine.

PRIOR ART On the other hand, in its conventional form the switch is of such large size that it has to be attached externally to the unit, in particular to the ram 01' prop, using bindings. Thismethod of attachment is a fixed one, and exposes the switch housing to the danger of mechanical damage.

OBJECT OF THE INVENTION It is the object of the invention to provide a design of control arrangement which can be miniaturised, i.e. its dimensions reduced to very small size, in order thus to make it possible to include plumb and switch housing in the structure of the pit prop unit, in particular in the pit prop head or ram, for example together with the hydraulic control elements for the pit prop itself, without requiring any appreciable degree of modification to pit prop in so doing.

BRIEF SUMMARY OF THE INVENTION In accordance with the invention, this object is achieved by virtue of the fact that two signal channels, together with a connection for the control medium, extend through a cover for the housing, on the inside face of which cover a plumb fulcrum pin is arranged, the control medium flowing through said pin, through two passages in the plumb and out of the latter into a slot formed between the plumb and the inside face of the housing cover into which slot the signal channels also open.

With this design of the control arrangement, the. supply and discharge arrangements for the control medium are located at the same side of the plumb so that the housing can be reduced in size to a very substantial extent. Therefore, it can be incorporated into hydraulic pit props and, in particular if made tubular in design, can be welded to the bottom part of the prop or to a protective cylinder surrounding same.

FURTHER FEATURES OF THE INVENTION It has been found convenient to aline the connection for the control medium with the fulcrum pin of the plumb.

In accordance with another feature ofthe invention, the two passages in the plumb terminate in kidney-shaped curved grooves which are recessed into that face of the plumb which is adjacent to the inside face of the housing cover. These grooves ensure that even if the pit prop should deviate a long way from its theoretical position, a signal will be produced and therefore the alining cylinder appropriately actuated.

The control arrangement thus designed makes it possible to accommodate the cover, together with a recess, in the head of the pit prop.

In another embodiment'of the invention, the cover is arranged upon a section of tube which, at that end opposite the housing, is fixed to the pit prop and forms between itself, the cover and this part of the pit prop, the housing proper.

The theoretical or set point position of the pit prop can be altered by rotating the cover because in this way the fulcrum pin of the plumbcan have its position relative to the axis of the pit prop altered. In order to provide some external indication of what particular setting has been made on the switch, it is preferred to arrange a scale between the housing and the housing cover.

BRIEF DESCRIPTION OF THE DRAWINGS An example of the invention will now be described with referenceto the accompanying drawings, in which:

FIG. 1 is a cutaway view of a hydraulic pit prop showing the welded on switch housing of the control arrangement according to the invention in end elevation;

FIG. 1a is a diagrammatic view showing the kidney-shaped grooves with relation to the signal-actuating passage in the normal position of the plumb.

FIG. 2 is a view corresponding to that of FIG. 1, with the housing cover removed;

FIG. 3 is a side elevation of the arrangement of FIG. 1, showing the components of the control arrangement in section.

DESCRIPTION OF PREFERRED EMBODIMENTS Welded to the external tube 1 of a hydraulic pit prop (of conventional design and therefore not explained in any further detail here), is a switch housing 2, tubular in the example illustrated. The housing is welded in position around its periphery, at 3 (FIG. 3). The housing has a cover 4 which is secured through the agency of an external screw thread 5 into a corresponding screw thread formed in the tubular housing 2. A projecting rim 6 on the housing cover, containing recesses 7, enables a tool to be located, for facilitating gripping of the housing cover 4, in order to screw it into the housing 2 into any desired specific angular position.

On that side 8 of the cover 4 which faces the interior of the housing, there is carried a pin 9 for a body serving as the plumb 10. This body is carried on the pin 9 through the agency of a ball bearing race 11. The pin 9 contains a coaxial bore 12 which terminates on the exterior side 14 of the cover 4 at a threaded connection '13 for an air pressure hose.

I Control air supplied via the connection 13 flows through the passage 12 and thence into two transverse branch passages 16 and 17 which have portions branching off at a right angle, one of which is marked 18 (FIG. 3). The branch passages lead at the points 19 and 20 into a slot 21 formed between the plumb 10 and the inside face 8 of the cover 4.

At the outside face 14 of the cover 4, there are two additional connections 24, 26, the one 26 being shown in section in FIG. 3. In order to be able to fit a hose connector, a thread 27 is provided. A passage 28 passes through the cover 4 so that a connection to the slot 21 is established.

The branch passages 16 and 17 terminate, in the example shown, in kidney-shaped curved grooves 30 and 31 which are recessed out of that surface 33 of the plumb 10 which faces the inside face 8 of the cover 4.

Control air, which is supplied to the control arrangement described at the point 13, passes into the two branch passages 16 and 17 and enters the said kidney-shaped grooves 30 and 31. With the pit prop in the nominally correct or set point position, the openingsof the passages 28 for the connections 24, 26, are located outside the area of the grooves 30, 31. Accordingly, no signal appears in either of the passages 24, 26.

With any deviation of the pit prop from the nominally correct position, one of the grooves 30 or 31, as the case may be, comes into alinement with one ofthe openings of the passages 28 associated with the connections 24 and 26. In this case, an adjusting or servo signal appears at the corresponding connection 24 or 26.

In the drawings, no detail has been shown of how this servo or adjusting signal is employed to actuate an alining cylinder, suffice it to say that when such signal appears the control error measured by the plumb is responsible in known manner for reproduction of a restoring force on the pit prop.

There is incorporated by reference US. Pat. No. 3,437,0l0, dated Apr. 8, 1969 of which applicant is a coinventor. This patent shows and describes a pendulurnlike device for controlling the operationjof rams for effecting angular adjustment of pit props. The purpose is to maintain the pit props alined to a predetermined position. The present invention constitutes an improvement over the structure shown in the patent because in the present structure it is possible to have the entire duct system arranged on one side of the housing enabling the housing to be miniaturized. As a consequence, the housing can have one side-fixed to the pit prop in a relative flat manner without interfering with other devices within the pit prop unit.

The Illustration also omits a scale which can, however, be arranged between the housing components 2 and 4 in order to display the angular position of the cover relative to the housing; This determines the relative position between the openings of the passages 28, and the kidney-shaped grooves 30, 31, and therefore the set point position of the control arrangement described.

The interior of the housing constituted by the components 2 and 4 and the external tube of the hydraulic pit prop has an air bleed facility at 40 in order to ensure that superatmospheric pressure does not develop inside the housing.

In departure from the example illustrated, the cover, together with a well formed in the pit prop, conveniently in the pit prop head the neighbourhood of the control elements of the pit prop itself, form the housing. The switch described is built into the pit prop. The switch can be reduced in size almost to an arbitrary extent and can consequently be incorporated into the pit prop at any convenient point.

I claim:

i. In a control system for adjusting the angular disposition of a pitprop arranged between the floor and ceiling of a mine shaft when the prop is at an angle to a predetermined line between the floor and ceiling, in which an extensible ram is disposed between the prop and a fixed support, a gravityresponsive device is provided for detecting the prop angularity, and means responsive to the gravity responsive device is provided for causing the ram to move the prop to such predetermined line, said gravity responsive device:

a housing'on the pit prop;

a cover closing one end of said housing;

a relatively movable plumb within said housing provided with a pair of bored passages;

a fulcrum pin pivotally supporting said plumb member having a passage communicating with said plumb member passages;

means for delivering pressure fluid to said fulcrum pin passage;

a pair of elongate curved grooves on the inner face of said plumb member communicating respectively with said bored passages; and

a pair of laterally spaced output ports in said cover for delivering pressure fluid to actuate said ram in one direction or the other in accordance with the inclination imparted to said plumb member.

2. The system as claimed in claim 1, in which the passage in said fulcrum pin extends longitudinally through same, and said pressure fluid delivery means comprises a passage through said cover.

3. The system as claimed in claim l, in which said housing is cylindrical, means for securing one end of said housing to a pit prop unit, and means for attaching said cover to the opposite end of said housing.

4. The system as claimed in claim 3, in which said cover attaching means comprises a rotatable mounting for enabling alternation of the set point of said plumb member. 

